From The Johns Hopkins University, Baltimore, Maryland, and Case Western Reserve University School of Medicine, Cleveland, Ohio.

Disclaimer: The authors of this article are responsible for its contents, including any clinical or treatment recommendations. No statement in this article should be construed as an official position of AHRQ or of the U.S. Department of Health and Human Services.

Acknowledgment: The authors thank Dr. Christine Chang, Task Order Officer, for her support throughout the project and for helpful suggestions for improving the clarity and presentation of the findings; Dr. Ari Eckerman and research assistants Drs. Elie Donath and Ghanshyam Palamaner Subash Shantha for their help in reviewing articles; Dr. Felicia Hill-Briggs for her consultation on quality-of-life outcomes; and the late Dr. Christopher Saudek for his contribution and guidance in the early stage of this work.

In randomized, controlled trials, MDI and CSII showed similar effects on hemoglobin A1c (HbA1c) levels and severe hypoglycemia in children or adults with type 1 diabetes mellitus and adults with type 2 diabetes mellitus. In adults with type 1 diabetes mellitus, HbA1c levels decreased more with CSII than with MDI, but 1 study heavily influenced these results. Compared with SMBG, rt-CGM achieved a lower HbA1c level (between-group difference of change, −0.26% [95% CI, −0.33% to −0.19%]) without any difference in severe hypoglycemia. Sensor-augmented insulin pump use decreased HbA1c levels more than MDI and SMBG did in persons with type 1 diabetes mellitus (between-group difference of change, −0.68% [CI, −0.81% to −0.54%]). Little evidence was available on other outcomes.

Limitation:

Many studies were small, of short duration, and limited to white persons with type 1 diabetes mellitus.

Conclusion:

Continuous subcutaneous insulin infusion and MDI have similar effects on glycemic control and hypoglycemia, except CSII has a favorable effect on glycemic control in adults with type 1 diabetes mellitus. For glycemic control, rt-CGM is superior to SMBG and sensor-augmented insulin pumps are superior to MDI and SMBG without increasing the risk for hypoglycemia.

Primary Funding Source:

Agency for Healthcare Research and Quality.

Tight glycemic control with intensive insulin therapy reduces the risk for diabetic microvascular and macrovascular complications (1–4). Innovations in insulin delivery and glucose monitoring are designed to improve glycemic control and quality of life (QOL) while limiting adverse effects, such as hypoglycemia and weight gain. These advances include continuous subcutaneous insulin infusion (CSII) and real-time continuous glucose monitoring (rt-CGM).

Although these technologies are widely used, their effectiveness has not been consistently demonstrated and the populations most likely to benefit are unclear. Health professionals and their diabetic patients need objective information when making decisions about these technologies, which may be expensive or heavily marketed. Such information is important to persons who decide on reimbursement policies and to companies developing new treatments and devices.

Intensive insulin therapy consists of CSII or multiple daily injections (MDI). Although most evidence indicates better glycemic control with CSII, its effect on other outcomes is less clear (5–8). A major limitation of previous reviews of CSII is the inclusion of studies that used regular insulin (5–7, 9), which offers less physiologic pharmacokinetics than insulin analogues (10–12). Rapid-acting insulin analogues are preferred for use with CSII, but whether rapid-acting analogue–based CSII confers additional benefit over currently used MDI strategies is unclear. Moreover, the benefits of CSII in children and older adults with type 1 diabetes mellitus have not been conclusively demonstrated.

Glucose monitoring is a critical part of insulin therapy, because patients can adjust their insulin doses and behavior on the basis of the results. Self-monitoring of blood glucose (SMBG) has been used with both MDI and CSII (13). Challenges that affect adherence to SMBG include pain, costs, behavioral and technical skills, motivation, and intrusiveness. Systems for rt-CGM have been developed to supplement SMBG.

A recent meta-analysis comparing SMBG with rt-CGM in adults and children with type 1 diabetes mellitus showed that the latter improved glycemic control, but there was no difference in the frequency of hypoglycemia; other nonglycemic outcomes were not reported (14). Current sensor-augmented pumps for insulin delivery (SAPs) combine rt-CGM technology with CSII (15). Pickup and colleagues' meta-analysis (14) did not compare SAP use with intensive insulin therapy and SMBG. To critically evaluate current evidence and fill in the literature gaps, we performed a systematic review to assess whether intensive insulin therapy (MDI vs. CSII) has a differential effect on outcomes in persons with type 1 or 2 diabetes mellitus and whether outcomes differ by monitoring strategy (SMBG vs. rt-CGM).

Methods

We followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines (16) and developed and followed a protocol for the review that was posted on the Agency for Healthcare Research and Quality (AHRQ) Web site (17). Questions for the review were refined on the basis of input from diabetes mellitus experts and public feedback. A comprehensive technical report that details the methods of the review and additional findings is available (17).

Data Sources and Searches

We searched for original studies in MEDLINE between 1966 and February 2012, EMBASE between 1974 and February 2012, and the Cochrane Central Register of Controlled Trials between 1966 and February 2012. Consistent with PRISMA guidelines (16), the detailed search strategies are reported in Appendix Table 1. Our search string included Medical Subject Headings and text terms related to diabetes mellitus, CSII, and continuous glucose monitoring and was not limited by language. We searched the reference lists of included articles and relevant reviews. We also searched ClinicalTrials.gov, a public registry of clinical trials, and contacted authors as needed.

Appendix Table 1.

Search Strategies

Appendix Table 1.

Study Selection

Two investigators independently reviewed citations for eligible studies. We included studies of adults, adolescents, or children with type 1 or 2 diabetes mellitus. We included studies comparing CSII with MDI (at least 3 injections per day), rt-CGM with SMBG (at least 3 fingersticks per day), or SAP use with MDI and SMBG. We excluded studies where regular insulin was used in the CSII group because this is not the preferred clinical practice (10–12). We included studies using long- and rapid-acting analogues or neutral protamine Hagedorn and regular insulin in the MDI groups, because both regimens are used in current practice.

We included randomized, controlled trials (RCTs) that evaluated process measures, intermediate outcomes, QOL, or severe hypoglycemia, and we included both RCTs and observational studies with a concurrent comparison group that evaluated microvascular or macrovascular outcomes or mortality. We excluded studies conducted in inpatient settings or that involved patients who used the device for less than 24 hours. If reviewers disagreed about inclusion after reviewing the full-text article, they discussed the article to finalize a decision.

We classified QOL measures as general health-related, diabetes mellitus–specific, and treatment-specific QOL. We included only validated measures (Appendix Table 2).

Appendix Table 2.

Health-Related QOL Assessment Tools Used in Each Category

Appendix Table 2.

Two reviewers independently assessed study quality. The assessment of RCTs was based on the Cochrane Collaboration's risk of bias tool (18) and the Methods Guide for Effectiveness and Comparative Effectiveness Reviews (19). The assessment of observational studies was based on the Downs and Black checklist (20).

Data Synthesis and Analysis

We critically appraised and qualitatively described characteristics of trials and conducted meta-analyses when there were at least 2 trials that were homogeneous with respect to population characteristics and study duration. For continuous outcomes, we calculated a weighted mean difference in change scores between groups by using a random-effects model with the DerSimonian and Laird formula (21).

We recorded the mean difference in outcome between groups, along with its measure of dispersion. If the study did not report this information, we calculated the point estimate of the mean difference in outcome by using the mean difference from baseline for each group or the baseline and final values for each group. We derived measures of dispersion by using standard methods (18).

If a study did not report the SD for the change from baseline, we imputed it by assuming a correlation coefficient of 0.5 (18). For crossover trials, we incorporated results only from the first period (19). If studies reported the incidence of hypoglycemia (that is, the number of patients who experienced hypoglycemia), we calculated a pooled fixed-effect Mantel–Haenszel odds ratio (22).

If studies reported event rates (that is, the number of events per patient during a period), we calculated a fixed-effect rate ratio in terms of the number of events per person-year (22). When 0 hypoglycemic events occurred in both groups, we calculated pooled fixed-effects Mantel–Haenszel odds ratios with continuity corrections of 0.001 (22). Similar results were obtained in sensitivity analyses with continuity corrections of 0.0001 or by using the double-arcsine transformation (23).

Heterogeneity among trials was tested by using a chi-square test (α ≤ 0.10) or I2 statistic (>50%) (24). In cases of substantial heterogeneity, we investigated by conducting meta-regression using such study characteristics as baseline HbA1c levels, patient age, or adherence to technology. We defined clinically meaningful between-group absolute differences as 0.5% for HbA1c (25), 30% for severe hypoglycemia (26), 15 mg/dL for fasting glucose (equal to 0.5% reduction in HbA1c levels) (27), 5 kg for weight (28), and an SD of 0.5 for QOL outcomes (29). Meta-analyses were conducted by using STATA, version 9.2 (StataCorp, College Station, Texas).

Grading of Evidence

We graded the strength of the evidence by adapting a scheme recommended in the Methods Guide for Effectiveness and Comparative Effectiveness Reviews (30). We applied evidence grades to the bodies of evidence about each intervention comparison for each outcome. We assessed the strength of the evidence by assessing its limitations, consistency, directness, precision, publication bias, and magnitude of effect.

Role of the Funding Source

The AHRQ reviewed the questions, protocol, and draft report but did not have a role in the literature search, analysis, or interpretation of findings. The authors prepared the manuscript, and the AHRQ granted copyright assertion.

Results

Study Characteristics

We included 33 studies in 37 articles, including 24 parallel RCTs and 9 randomized crossover trials (Appendix Figure 1). Nineteen studies compared the effects of MDI with those of CSII, 10 studies compared the effects of rt-CGM with those of SMBG, and 4 studies compared the effects of SAP use with those of MDI and SMBG. In searching ClinicalTrials.gov, we identified 4 additional studies for our comparisons—2 were completed, but results were not published; the other 2 are ongoing.

* Total number of articles may exceed the number in the corresponding box because articles could be excluded for more than 1 reason.

We found no RCTs or observational studies that reported on long-term microvascular or macrovascular outcomes. Ten studies were conducted in North America, 14 in Europe, 2 in the Middle East, and 1 in Australia; 6 did not mention location. Study duration ranged from 12 to 52 weeks. Pharmaceutical company support was reported in 24 articles (Appendix Table 3). Table 1 summarizes the main findings. Many studies had significant risk of bias because their methods of handling random assignment of participants was unclear, and very few had any blinding of outcome assessment (see Appendix Table 4 for details).

Appendix Table 3.

Population Characteristics of Studies Comparing Methods of Insulin Delivery or Glucose Monitoring for Diabetes Mellitus

Appendix Table 3.

Table 1.

Summary of Findings and Strength of Evidence Comparing Insulin Delivery and Glucose-Monitoring Methods for Reported Outcomes

Table 1.

Appendix Table 4.

Comparative Effectiveness of CSII Versus MDI

Children and Adolescents With Type 1 Diabetes Mellitus

Seven studies compared MDI with CSII in children and adolescents with type 1 diabetes mellitus (31–37).

HbA1c Level.

Figure 1 shows the comparative effectiveness of CSII versus MDI, where strength of evidence was moderate. Our meta-analysis showed no difference between groups in the HbA1c level change from baseline after 16 or more weeks of follow-up. Results were similar among adolescents older than 12 years (combined mean between-group difference in change from baseline in HbA1c, −0.10% [95% CI, −0.48% to 0.27%]; I2 = 0%) and less precise among children aged 12 years or younger (combined mean between-group difference in change from baseline in HbA1c, −0.05% [CI, −1.01% to 0.96%]; I2 = 0%) (Appendix Table 5). One (32) of the 7 studies was of good quality; all 7 studies had medium risk of bias.

Figure 1.

Mean between-group difference in the change from baseline HbA1c comparing CSII with MDI among children and adolescents with T1DM, adults with T1DM, and adults with T2DM.

Summary of the Evidence of the Comparative Effectiveness of CSII With MDI, rt-CGM With SMBG, and SAP Therapy With MDI and SMBG in Children, Adolescents, or Adults With T1DM or T2DM

Appendix Table 5.

Severe Hypoglycemia.

We excluded 1 study (32) from the meta-analysis because it reported the hypoglycemia rate only in the MDI group. Strength of evidence was low for CSII versus MDI; our meta-analysis found a similar rate of severe hypoglycemia in the 2 intervention groups, although the CI was wide (Figure 2). The risk reduction favoring CSII was 9 events per 1000 patients, with a wide CI ranging from 118 fewer events to 100 more events per 1000 patients. Results were similar in our meta-analysis of 3 RCTs in adolescents and of 2 RCTs in children aged 12 years or younger, although the estimate was less precise in the latter (Appendix Table 5). None of these 5 studies was of good quality, and all 5 had medium risk of bias.

Figure 2.

Pooled IRR for severe hypoglycemia comparing CSII with MDI among children and adolescents with T1DM.

Other Glycemic Outcomes.

Continuous subcutaneous insulin infusion and MDI generally had similar effects on daytime, nocturnal, or mild hypoglycemia and weight gain. However, for most subgroups, the strength of evidence was low, primarily because of imprecise results (Table 1). Data were insufficient to draw conclusions on the effect of CSII and MDI on hyperglycemia. Risk of bias was medium to high in the small number of studies reporting these outcomes, and there were no good-quality studies (Appendix Tables 4 and 5).

QOL.

Six studies (31–34, 36, 37) examined the comparative effectiveness of CSII versus MDI on QOL in children and found similar effects on general QOL (33, 34) and better satisfaction with CSII (36, 37) (Appendix Tables 4 and 5). Different instruments measured outcomes; strength of evidence was low, with medium risk of bias and only 1 good-quality study (32).

Adults With Type 1 Diabetes Mellitus

HbA1c Level.

Our meta-analysis showed that CSII decreased HbA1c levels more than MDI did, with low strength of evidence (combined mean between-group difference, −0.30% [CI, −0.58% to −0.02%]; I2 = 64.5%) (Figure 1). However, the pooled estimate was influenced by 1 study (40) in which participants had a higher HbA1c level at enrollment (9.3%) compared with that of the other studies (7.7% to 8.2%) (39, 45), resulting in greater opportunity for a large decrease in HbA1c levels in that study (−0.84%) than in the other studies (−0.1% to 0.25%). The difference between CSII and MDI became null (combined mean between-group difference, −0.01% [CI, −0.35% to 0.34%]; I2 = 0%) after this study was removed. Two of the studies (41, 45) were good quality, with medium risk of bias in all 4 studies.

Severe Hypoglycemia.

All 8 studies evaluated severe hypoglycemia. One study (45) was excluded from meta-analysis because it reported only the number of severe hypoglycemic events. In our meta-analysis of 3 RCTs that defined severe hypoglycemia as requiring third-party assistance, CSII and MDI had a similar incidence but the CI was wide (39, 40, 44) (Figure 3). The risk reduction favoring CSII was 38 events per 1000 patients, with a CI ranging from 142 fewer events to 66 more events per 1000 patients. Our meta-analysis excluded 4 crossover trials that did not provide quantitative results by period (38, 41–43) (Appendix Table 5); results were mixed: One trial favored CSII (43), 1 favored MDI (41), and 2 showed no between-group differences (38, 42). The overall strength of evidence was low, with 2 good-quality studies (41, 45) and medium risk of bias in the 8 studies.

Figure 3.

Pooled OR for severe hypoglycemia comparing CSII with MDI among adults with T1DM.

Other Glycemic Outcomes.

The incidence of symptomatic hypoglycemia was higher with CSII than with MDI, but the strength of evidence was low; there was significant statistical heterogeneity, medium risk of bias, and 1 good-quality study (45). Six studies evaluated the incidence of other types of mild hypoglycemia (38–43), but definitions varied and strength of evidence was low, with medium risk of bias and 1 good-quality study (41).

Four studies reported no difference in nonsevere hypoglycemia, 1 reported higher risk for mild hypoglycemia with CSII than with MDI (40), and another reported an increased risk for self-managed mild hypoglycemia with MDI (43). The strength of evidence generally was insufficient to draw firm conclusions about other symptomatic hypoglycemia, daytime hypoglycemia, nocturnal hypoglycemia, or fasting glucose levels.

Weight Gain.

Weight gain was similar between the CSII and MDI groups. However, the strength of evidence was low, with medium risk of bias in 4 studies and no good-quality studies (Appendix Tables 4 and 5) (38, 40, 44, 46).

QOL.

Three studies showed improved diabetes mellitus–specific QOL favoring CSII (39, 43). However, the strength of evidence was low, with high risk of bias and 1 good-quality study (Appendix Tables 4 and 5) (44).

Severe Hypoglycemia.

The incidence of severe hypoglycemia did not differ much between CSII and MDI in our meta-analysis of 2 studies (48, 50), but the CI of the difference was wide (Appendix Table 5). The strength of evidence was low because of imprecision, medium risk of bias and no good-quality studies.

Weight Gain.

Weight gain did not differ between CSII and MDI, with low strength of evidence, high risk of bias in 2 studies (48, 49), and no good-quality studies (Appendix Tables 4 and 5).

Evidence was insufficient to make conclusions about the effects of CSII versus MDI on nocturnal hypoglycemia, hyperglycemia, or QOL in adults with type 2 diabetes mellitus.

Comparative Effectiveness of rt-CGM Versus SMBG

All 10 trials addressing the comparative effectiveness of rt-CGM versus SMBG were conducted in patients with type 1 diabetes mellitus (51–60). None of the studies reported on mortality or any of the process measures. The insulin delivery method was CSII in 5 studies (51–53, 55, 57) and either MDI or CSII in the other 5 studies (54, 56, 58–60).

HbA1c Level

Two studies were excluded from our meta-analysis because of heterogeneity in study design. One had a crossover design (51) but did not report results by study period. The other study (52) was excluded because it compared SAPs with CSII and SMBG.

Our meta-analysis of 8 trials (10 estimates, because 2 studies had >1 subgroup) of at least 12 weeks in duration showed that rt-CGM reduced HbA1c levels more than SMBG did (Figure 4, top). The analysis suggested statistical heterogeneity (I2 = 69.9%; P = 0.000), but no study influenced results substantially. The heterogeneity was explained in part by percentage of adherence to sensor use. In metaregression, we found that sensor adherence was associated with HbA1c level reduction (r = −0.858; P = 0.007) (Appendix Figure 2). In a sensitivity analysis that included only studies with a rate of adherence to sensor use higher than 60%, the rt-CGM group had an even greater reduction in HbA1c levels than SMBG (Table 2). Strength of evidence was high, risk of bias was low, and 6 studies (52, 54, 55, 57, 58, 60) were good-quality.

Figure 4.

Comparison of rt-CGM with SMBG and SAP use with MDI plus SMBG among patients with T1DM.

Summary of the Subgroup Analyses in the Between-Group Change From Baseline HbA1c Among Patients With T1DM Comparing rt-CGM with SMBG

Table 2.

Five trials reported data separately for younger age groups. One study (58) reported a significant effect of rt-CGM compared with SMBG for persons aged 8 to 18 years. The other 4 trials showed no significant decrease in HbA1c levels, but all favored rt-CGM (56, 57, 59–61).

Our meta-analysis of 5 studies in patients aged 18 years or younger showed no mean between-group difference in change from baseline HbA1c level favoring rt-CGM (Table 2). We performed a subsidiary analysis for 3 studies (56, 57, 59) that reported data separately for adults. Our meta-analysis of these 3 studies showed a between-group mean difference in HbA1c levels; however, heterogeneity was significant (Table 2). Three other studies did not present results separately for adults and children and were excluded from this subsidiary meta-analysis (53–55).

Severe Hypoglycemia

Nine studies reported the incidence of severe hypoglycemia (52–60). In our meta-analysis, the incidence of severe hypoglycemia did not differ between rt-CGM and SMBG (pooled relative risk, 0.88 [CI, 0.53 to 1.46]) (Figure 4, bottom). The risk difference between 2 groups favoring rt-CGM was 6 events per 1000 patients, with a CI ranging from 31 fewer events to 19 more events per 1000 patients. The strength of evidence was low, with medium risk of bias and 6 good-quality studies (52, 54, 55, 57, 58, 60). Three trials reported data on severe hypoglycemia in a pediatric population (52, 56, 60), but 1 trial showed less hypoglycemia by using rt-CGM (52), whereas the other studies showed no difference (56, 60).

Appendix Figure 4.

Between-group difference between rt-CGM and SMBG in time spent in hyperglycemic range changed from baseline among patients with T1DM.

Boxes indicate individual study point estimates. The box size denotes the weight of the study, with larger boxes contributing more to the pooled estimate. The width of the horizontal lines represents the 95% CI for each study. The diamond at the bottom of the figure indicates the 95% CI for the random-effects pooled estimate. Test for heterogeneity: Q = 5.80 (P = 0.33). rt-CGM = real-time continuous glucose monitoring; SMBG = self-monitoring of blood glucose; T1DM = type 1 diabetes mellitus.

* Patients aged >25 y.

† Patients aged 8–14 y.

‡ Patients aged 15–24 y.

QOL

Four studies compared QOL with rt-CGM versus SMBG (51, 52, 60, 62). Although QOL was measured by using different instruments, all studies reported no difference between groups. Strength of evidence was low, with low to medium risk of bias and 3 good-quality studies (52, 60, 62).

Comparison of SAP Versus MDI or SMBG

Four studies evaluated a SAP versus MDI and SMBG in children and adults with type 1 diabetes mellitus (63–66). All 4 studies used the MiniMed Paradigm REAL-Time Revel System (Medtronic, Northridge, California) and provided training in use of the device (63–66).

HbA1c Level

Our meta-analysis of 4 RCTs showed that the SAP decreased HbA1c levels more than MDI or SMBG did (combined mean between-group difference from baseline, −0.68%) (Figure 2, top). One (63) of the 4 studies included in our meta-analyses was much larger than the other 3 and dominated the results. Strength of evidence was moderate, risk of bias was medium, and 2 studies (63, 66) were good quality.

Hyperglycemia

In 2 studies (63, 66), the time spent with hyperglycemia was significantly shorter with the SAP than with MDI or SMBG (P < 0.001). Heterogeneity in defining hyperglycemia did not permit pooling of results.

Severe Hypoglycemia

Four studies reported on the incidence of severe hypoglycemia, but use of different measures precluded a pooled analysis (Appendix Table 5). In the largest trial (63), severe hypoglycemia occurred at a similar rate in the SAP and MDI or SMBG groups (21 out of 247 vs. 17 out of 248; P = 0.58) with a risk difference of 1.6% (CI, −3.0% to 6.3%). Strength of evidence was moderate, risk of bias was medium, and 2 studies (63, 66) were good quality.

Included studies provided moderate strength of evidence for the effects of rt-CGM plus CSII versus MDI or SMBG on nonsevere hypoglycemia and hyperglycemia. However, these studies provided insufficient to low strength of evidence for weight and QOL (Appendix Table 5).

Applicability of Evidence and Publication Bias

Most studies did not report the racial and ethnic composition of the study populations; however, for those that did, more than 80% of participants were white. Few studies included patients younger than 12 years or older than 65 years. The small numbers of studies did not allow us to make conclusions about publication bias.

Discussion

Comparative Effectiveness of CSII Versus MDI

Our review showed that CSII and MDI have similar effects on glycemic control and the incidence of severe hypoglycemia in children and adolescents with type 1 diabetes mellitus and in adults with type 2 diabetes mellitus. In adults with type 1 diabetes mellitus, CSII showed favorable effects on glycemic control. However, the result was influenced by 1 study in which participants had higher HbA1c levels at enrollment, allowing for a greater decrease in HbA1c levels than that of other studies, where participants were closer to the target HbA1c level at enrollment (40). Compared with MDI, CSII yielded better satisfaction with diabetes mellitus treatment in children with type 1 diabetes mellitus and better diabetes mellitus–specific QOL in adults with type 1 diabetes mellitus, but the strength of evidence on QOL effects was low. The evidence was insufficient to draw definitive conclusions about other nonglycemic outcomes.

Our systematic review complements and extends previous meta-analyses on the comparative effectiveness of CSII versus MDI by including more studies of persons with type 2 diabetes mellitus (5–7, 9, 67); including only studies using rapidly acting insulin analogues in the CSII groups (5–7, 9); and requiring the MDI groups to receive at least 3 injections per day, the current standard for intensive insulin therapy (6, 8, 67, 68). Although some meta-analyses have shown a significant reduction in HbA1c levels with CSII, none reached what is considered a clinically meaningful difference of 0.5% (25). Previous meta-analyses that have shown larger effect sizes favoring CSII have included before-and-after studies that were vulnerable to selection bias and confounding (5). Some analyses included fewer than 3 daily injections in the MDI group, which may have biased the results to favor CSII (8, 67).

Similar to a previous meta-analysis, we found that severe hypoglycemia rates in persons with type 1 diabetes mellitus were similar between MDI and CSII groups (68). Although 2 analyses found a higher rate of severe hypoglycemia with MDI than with CSII, 1 analysis included only studies in which participants reported an increased frequency of baseline severe hypoglycemia, which may have resulted in a greater likelihood of improvement (5). The other analysis included studies using regular insulin in the CSII groups, which would be expected to result in less hypoglycemia than regular insulin with MDI because of steadier insulin delivery (7). Our meta-analysis is distinct from previous reviews because it includes heretofore unreported studies that use current rapid-acting analogues in the CSII groups (9) and provides a quantitative effect estimate (25).

Comparative Effectiveness of rt-CGM Versus SMBG

Our review of the comparative effectiveness of rt-CGM and SMBG complements a recent meta-analysis (14) by including a comprehensive set of outcomes. Compared with SMBG, rt-CGM achieved a lower HbA1c level (absolute difference, −0.26%) that was significant but below the 0.5% difference that we defined as clinically meaningful. A sensitivity analysis showed that this effect was slightly greater in studies where sensor adherence was 60% or more (−0.36%). We also found that rt-CGM was associated with a lower HbA1c level than MDI in persons aged 18 years or younger.

The intervention groups did not differ in the rate of severe hypoglycemia, the fear of which can be a barrier to glycemic control. A few studies that evaluated weight gain or QOL found no difference between intervention groups. These findings provide modest support for recommendations to use rt-CGM in children older than 8 years (69).

Comparative Effectiveness of SAP Versus MDI or SMBG

Sensor-augmented insulin pump use resulted in a statistically and clinically significant greater reduction in HbA1c levels than with MDI or SMBG in persons with type 1 diabetes mellitus. The evidence was insufficient to draw definitive conclusions about severe hypoglycemia or QOL. No previous meta-analysis examined this comparison.

Limitations

Our review highlights important weaknesses in the literature. Most RCTs of devices that deliver insulin and monitor glucose levels were small, with the largest having 322 participants (36). Most studies were fair- to poor-quality and did not report most quality items of interest. Most studies did not report the racial and ethnic composition of the study samples. For those that did, most participants were white. Few studies included children younger than 12 years or adults older than 65 years. This is probably because type 1 diabetes mellitus is less prevalent in minority and elderly persons, making it less feasible to perform studies in these subpopulations.

The studies were heterogeneous in definitions of hypoglycemia, hyperglycemia, and weight gain, making it difficult to combine data across studies. None of the studies included data on long-term micro- or macrovascular complications. These complications develop over many years, and the longest follow-up among the studies was 52 weeks. Data on these outcomes would be ideal but would require a large RCT several years in duration that could sustain clinically meaningful HbA1c level reductions; this RCT may not be feasible, particularly because persons may switch therapies over time.

Other than the rt-CGM studies, most studies did not report on treatment adherence. The high baseline HbA1c levels in the CSII and MDI groups in many studies may indicate poor adherence to previous as well as intervention treatments, which may have biased results to the null (although there is also greater room for improvement). Finally, the studies were heterogeneous in assessing QOL, which prevented us from quantifying the effects on QOL.

Our review had several limitations. Meta-analyses in general are subject to bias based on article selection criteria, multiple comparisons, and the state of the literature. We reviewed studies of current methods for intensive insulin therapy and glucose monitoring. However, there were few studies for each of the comparisons and publication bias could not be definitely excluded. We may have missed unpublished studies on this topic, but our search strategy was comprehensive and included non–English-language publications.

Our data are not generalizable to all patients with diabetes mellitus, because management of CSII and rt-CGM is often limited to expert settings and highly motivated patients. All studies of rt-CGM are subject to ascertainment bias because rt-CGM provides more data on hypo- and hyperglycemia than on SMBG alone. Because blinding patients in an RCT comparing CSII with MDI or comparing rt-SGM with SMBG is not feasible, studies of QOL outcomes could have been vulnerable to reporting bias if patients believed that CSII and rt-CGM were superior. Because of the small number of studies in each targeted population, we could not adjust the analyses for all potential effect modifiers, such as baseline HbA1c level, diabetes mellitus duration, and age.

Finally, our study did not address availability, costs, or insurance coverage of CSII, rt-CGM, and SAPs, which may be obstacles to their use. In general, insulin pumps cost between $6000 and $7000, and supplies cost approximately $2000 per year. Real-time continuous glucose monitoring costs approximately $5000 per year. The extent to which insurance covers these costs will contribute to their use in practice.

Implications

Our findings indicate that MDI and rapid-acting analogue–based CSII are similarly effective in lowering HbA1c levels with similar rates of hypoglycemia in patients with type 1 diabetes mellitus. From a patient-focused perspective, CSII yielded better satisfaction with diabetes mellitus treatment in children with type 1 diabetes mellitus and better diabetes mellitus–specific QOL in adults with type 1 diabetes mellitus. These data suggest that the approach to intensive insulin therapy can be individualized to patient preference and maximize treatment satisfaction and QOL, because both MDI and rapid-acting analogue–based CSII have similar effectiveness for glycemic control.

This is the first systematic review to examine the comparative effectiveness of both rt-CGM versus SMBG and the SAP versus MDI or SMBG. Our findings indicate that rt-CGM is superior to SMBG in lowering HbA1c levels without increasing the risk for severe hypoglycemia in persons with type 1 diabetes mellitus, particularly those who are adherent to the monitoring device. Even though CSII and MDI without rt-CGM have similar effects on HbA1c levels, addition of rt-CGM to CSII is superior to MDI and SMBG in decreasing HbA1c levels. Thus, the addition of this monitoring method to SMBG and intensive insulin therapy can assist in achieving glycemic targets in type 1 diabetes mellitus. The literature does not allow us to determine the comparative effectiveness of rt-CGM versus SMBG in patients using only CSII or MDI because the modes of insulin therapy were mixed in the studies.

Future research should include larger studies in populations in which diabetes mellitus is increasing (elderly persons, persons with insulin-requiring type 2 diabetes mellitus, and minority populations). Studies should report on important clinical outcomes, consider effects of adherence on outcomes, and assess cost-effectiveness.

The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. The Diabetes Control and Complications Trial Research Group.

Higgins JPT, ed. Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0. The Cochrane Collaboration. 2011. Accessed at www.cochrane-handbook.org on 1 March 2012.

Agency for Healthcare Research and Quality. Methods Guide for Effectiveness and Comparative Effectiveness Reviews. Rockville, MD: Agency for Healthcare Research and Quality; 2011. Accessed at www.effectivehealthcare.ahrq.gov/methodsguide.cfm on 1 March 2012.

Downs

SH

,

Black

N

.

The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions.

Improved treatment satisfaction but no difference in metabolic control when using continuous subcutaneous insulin infusion vs. multiple daily injections in children at onset of type 1 diabetes mellitus.

Comparison of continuous subcutaneous insulin infusion and multiple daily injection regimens using insulin lispro in type 1 diabetic patients on intensified treatment: a randomized study. The Study Group for the Development of Pump Therapy in Diabetes.

Comparison of the effects of continuous subcutaneous insulin infusion (CSII) and NPH-based multiple daily insulin injections (MDI) on glycaemic control and quality of life: results of the 5-nations trial.

Table 1.

Appendix Table 4.

Summary of the Evidence of the Comparative Effectiveness of CSII With MDI, rt-CGM With SMBG, and SAP Therapy With MDI and SMBG in Children, Adolescents, or Adults With T1DM or T2DM

Appendix Table 5.

Table 2.

Summary of the Subgroup Analyses in the Between-Group Change From Baseline HbA1c Among Patients With T1DM Comparing rt-CGM with SMBG

Table 2.

Clinical Slide Sets

Terms of Use

The In the Clinic® slide sets are owned and copyrighted by the American College of Physicians (ACP). All text, graphics, trademarks, and other intellectual property incorporated into the slide sets remain the sole and exclusive property of the ACP. The slide sets may be used only by the person who downloads or purchases them and only for the purpose of presenting them during not-for-profit educational activities. Users may incorporate the entire slide set or selected individual slides into their own teaching presentations but may not alter the content of the slides in any way or remove the ACP copyright notice. Users may make print copies for use as hand-outs for the audience the user is personally addressing but may not otherwise reproduce or distribute the slides by any means or media, including but not limited to sending them as e-mail attachments, posting them on Internet or Intranet sites, publishing them in meeting proceedings, or making them available for sale or distribution in any unauthorized form, without the express written permission of the ACP. Unauthorized use of the In the Clinic slide sets will constitute copyright infringement.